Apparatus and method for continuous nitration



Sept. 6, 1960 c. D. MCKINNEY, JR 2,951,866

APPARATUS AND METHOD FOR commuous NITRATION Filed Sept. 28, 1956 unmmc ACID TUBULAR fil T g gm LIQUID POLYHYDRIC 22 ALCOHOL TUBULAR REACTOR TUBULAR /26 ooounc NHL SEPARATING ZONE 21 i FIG. I I; s i

CHARLES I). No KINNEY JR. INVENTOR.

APPARATUS AND METHOD FOR CONTINUOUS NITRATION Charles D. McKinney, In, Cumberland, Md assignor t Hercules Powder Company, Wilmington, Del., a corporation of Delaware Filed Sept. 28, 1956, Ser. No. 612,832

8 Claims. (Cl. 260-467) The present invention relates to an improved process and apparatus for the continuous manufacture of explosive liquid nitric acid esters of rapidly esterfiable liquid polyhydric alcohols, and more particularly for the continuous manufacture of nitroglycerin, nitroglycols, and the like. I

Heretofore, various methods for the continuous manufacture of explosive liquid nitric acid esters have been proposed because such methods inherently should be less hazardous and more economical than the well-established and conventional batch process for manufacturing these explosive compounds. Heretofore, however, previously proposed continuous nitration processes have always involved various mechanical mixing devices in the nitrating zone to eflfect intimate mixing of the nitrating acid with the liquid alcohol. Such mechanical devices in the nitrating zone always involve the element of hazard when dealing with highly sensitive materials such as nitroglycerin and the like. Moreover, extensive circulation, recirculation, and a relatively long residence time of the reaction mixture in the nitrating zone is a characteristic of a majority of the previously proposed methods, and such features are inherently undesirable because they favor side reactions.

It is, therefore, the principal object of the present invention to provide an improved process and apparatus for the continuous manufacture of explosive liquid nitric acid esters having great diversity for overcoming the various undesirable features of prior art methods and apparatus. Among the objectives accomplished in accordance with this invention are the following:

Provision of a method and apparatus which are unique in their simplicity in comparison to prior art methods;

Provision of a method and apparatus wherein there is a minimum of side reaction encountered, and an exceptionally pure product is obtained;

Provision of a method and apparatus wherein there is a minimum amount of explosive liquid nitric acid ester in process at any time;

Provision of a method and apparatus wherein positive control of the process is easily and readily accomplished;

Provision of a method and apparatus which requires only simple, relatively inexpensive equipment and buildings in comparison to prior art methods.

Other objects of the invention will appear hereinafter, the novel features and combinations being set forth in the appended claims.

Generally described, the continuous manufacture of explosive liquid nitric acid esters of polyhydric alcohols in accordance with this invention comprises continuously feeding a stream of polyhydric alcohol through a tubular path to a tubular reaction zone, simultaneously and continuously feeding a stream of precooled nitrating acid through a second tubular path to said tubular reaction 2,951,866 patented Sept. 6, 1960.

advancing the resultant reaction mixture stream through the tubular reaction zone at a flow rate corresponding to a Reynolds Number of at least about 1000 until substantially all of the polyhydric alcohol has reacted with the nitrating acid to form explosive liquid nitric acid ester, and thereafter separating explosive liquid nitric acid ester of polyhydric alcohol from spent nitrating acid.

In a preferred embodiment of the invention, the tubular reaction zone is uncooled and the temperature of the reaction mixture in the tubular reaction zone is controlled within safe operating limits by regulating the temperature of the precooled nitrating acid and by regulating. the proportions, respectively, of the nitrating acid and of the polyhydric alcohol which are mixed together by impingement to form the reaction mixture. Operating, with an uncooled tubular reaction zone promotes a more: rapid reaction which is desirable, and in fact is an im-- portant advantage of the present invention. Moreover,. although not necessary in practicing this invention, it has; been found desirable to cool the mixture of explosive: liquid nitric acid ester and spent nitrating acid upon com-- pletion of the nitration reaction and prior to separation, since this promotes a more complete recovery of the; product. While cooling can be effected in a separate vessel following discharge of the reaction mixture from the tubular reaction zone, such cooling is more conveniently and efficiently accomplished in a tubular cooling zone forming an extension of the tubular reaction zone. Preferably, but not necessarily, the reaction mixture stream is advanced through the tubular reaction zone, and the tubular cooling zone when employed, at a flow rate corresponding to a Reynolds Number of at least about 2,100 and sufficient to maintain turbulent flow in the reaction mixture.

Improved apparatus for practicing continuous manufacture of explosive liquid nitric" acid esters in accordance with this invention comprises in combination an elongated tubular reactor having a first communicating feed tube and a second communicating feed tube, said feed tubes converging and junctioning with said tubular reactor at one end thereof, the other end of said tubular reactor being disposed to discharge into a separating zone, said first feed tube communicating with a polyhydric alcohol supply source and having means associated therewith for feeding a stream of polyhydric alcohol at predetermined flow rate through said first feed tube to the tubular reactor, said second feed tube communicating with a nitrating acid supply source and having means associated therewith for feeding a stream of nitrating acid at predetermined flow rate through said second feed tube to the tubular reactor and means for cooling the nitrating acid.

Whereas the preferred practice of this invention employs an uncooled .tubular reaction zone, and thereforea tubular reactor free of cooling means, the invention is by no means limited in this respect, for the invention can also be practiced satisfactorily with a tubular reactor, all or part of which is associated with cooling means. It has already been pointed out hereinbefore that, according to a preferred embodiment of the invention, it is both convenient and practical to cool the reac-- I tion mixture, upon completion of the nitration reaction.

zone, causing the separate streams of polyhydric alcohol and precooled nitrating acid to impinge upon each other at sufl'icient flow rates to form a turbulent reaction mixture stream in the tubular-reaction zone, continuously in an uncooled tubular reaction zone and before sep-- aration, in a tubular cooling zone forming an extension; of the tubular reaction zone. Accordingly, the tubular reactor for practicing this embodiment of the invention.

is free of cooling means adjacent the end thereof which junctions with the two feed tubes and has cooling means associated with at least part'thereof adjacent the discharge end. I It is an important characteristic of this invention that there are-no moving parts, obstructions, or constrictions in the tubular reactor. Turbulent flow, brought about by impinging the two reactant streams upon each other at sufficient flow rates, is relied upon as the sole means for eflectuating intimate dispersion of the polyhydrie al: cohol in the nitrating acid, and for maintaining the reaction mixture in emulsified form in the. tubular reactor. It is a further characteristic of this invention that the reaction mixture positively and continuously advances through the tubular reactor without recirculation, and residence time of the reaction mixture in the tubular reactor is limited to only a few seconds, sufiicient to complete the nitration reaction, and cool the product if de-. sired, before discharging the reaction mixture stream into the separating zone.

A preferred embodiment of the invention. has been chosen for purposes of illustration and description and is shown in the, accompanying drawing forming a part of the specification wherein reference symbols refer to like parts wherever they occur, and wherein gages'and other conventional auxiliary equipment have been omitted for the sake of simplicity. V

Fig. l is a diagrammatic drawing illustrating the features of this invention.

Fig. 2 is a fragmentary cross-sectional view illustrating one embodiment for the junction of the two tubular reactant feed lines with the tubular reactor of this invention.

Referring to the drawing, liquid polyhydric alcohol from supply tank 1 1 via valved line 12 is fed through metering pump 13 in predetermined proportions via line 14 to tubular reactor 15. Simultaneously nitrating acid from supply tank 16 via valved line 17 is fed through pump 18 in predetermined proportions via line 19, tubular nitrating acid cooling coil 21, and valved line 24 to tubular reactor 15 22 is a conventional heat exchange means such as a refrigerating brine bath or the like. Although it is convenient to cool the nitrating acid as illustrated, the invention is not limited in this respect. The only requirement is that the nitrating acid should be cooled before it enters the tubular reaction zone. Accordingly, therefore, cooling means can be employed to cool the nitrating acid at any desirable and convenient point along the path of flow of nitrating acid in the system before the nitrating acid reaches the reaction zone. For example, the nitrating acid can be cooled at-supply tank -16, or even at some point before the acid reaches supply tank 16. Valve 23 in line 24 is a throttle valve for regulating the flow of nitrating acid when employing a centrifugal pump. Valve 23 becomes unnecessary when, a metering pump or similar constant feed means is employed instead of a centrifugal pump.

Valve 29 in line 14 is a quick opening by-pass valve which is normally closed. However, in case of an emergency shutdown, this valve can be instantly opened to. shut off the supply of alcohol to the reaction zone and return the alcohol stream via line '31 to alcohol supply tank 11. Such a quick opening by-pass valve normally is not employed in the nitrating acidline, since in case.

of an emergency shutdown, nitrating acid is employed to sweep out the tubular reactor.

It will be seen from the drawing that feed lines 14 and 24 converge and junction with tubular reactor 15 at one end thereof, and in the embodiment illustrated, the two feed lines and the tubular reactor form a simple- T tube section, free of moving parts, obstructions, or constrictions, as illustrated in Fig. 2. The separate streams of polyhydric alcohol and pre-cooled nitrating acid thus converge and impinge upon each other at the point where the two feed lines junction with the tubular reactor.

The invention is not limited to employment of. a T tube, however, sincethe only requirement is that the feed lines converge and junction with the tubular reactor so that the feed streams of polyhydric alcohol and nitrating acid will impinge upon each other, Accordingly, any

7 tion and frequent adjustment.

pirator requires that friction losses of head between the geometrical configuration for the junction of the feed lines with the tubular reactor which will accomplish the purposes of this invention is within the scope of this invention.

The rates of flow of the reactant streams are regulated so that upon impinging upon each other they form a turbulent reaction mixture wherein the polyhydric alcohol is intimately dispersed in emulsion form throughout the nitrating acid. No further mixing is required. This is indeed surprising, since heretofore it has been considered necessary to providemechanical stirring devices. The present invention, on the other hand, relies solely on turbulent flow created by impinging the reactant streams upon each other at flow rates sufficient to initiate turbulen flow in the resulting reaction mixture.

Advantages of the present invention in comparison to prior art methods and apparatus employing mechanical stirring devices to disperse the polyhydric alcohol in the nitrating acid reside in more rapid'and uniform dispersion, improved control, and greatly improved safety. In comparison to aspirators of the Venturi type, one important advantage of the present invention resides in control. An aspirator relies on vacuum to suck or pull the relatively viscous liquid polyhydric alcohol into the jet stream of nitrating acid Accordingly, variations in temperature of the polyhydric alcohol or variations in the velocity of the jet stream materially affect flow of the alcohol stream. To overcome such variations, a throttle valve must be employed in the alcohol line to adjust and regulate flow, and requires constant attention and frequent adjustment. On the other hand, alcohol feed from a metering pump in accordance with a preferred embodiment of this invention does not require constant atten- Moreover, since an as- Venturi and the discharge be low, it is necessary to employ short, substantially straight transport lines in the region between the Venturi and the discharge for satisfactory operation. Accordingly, transport of the reaction mixture through an integral cooler coil, or any long lines between the Venturi and the discharge would entail sufficient downstream friction'losses of head to seriously impair or even prevent satisfactory operation of the as.- pirator. Furthermore, it has been definitely established that the nitration reaction is only partly completed in the aspirator, itself. Accordingly, provision must be made for completing the reaction in an auxiliary vessel under controlled temperature conditions before discharging to a separating zone. The present invention, on the other hand, is not burdened with theseshortcomings.

According to the present invention, the turbulent reaction mixture is then advanced through. the tubular reactor 15 at a flow rate corresponding to a Reynolds Number of at least about 1,000, preferably at a flow rate corresponding to a Reynolds Number of at least about 2,100 suflicient to maintain turbulent flow in the reaction mixture, and is discharged at 2.7 into a separatingzone 28 where the explosive liquid nitric acid ester is separated from the spent nitrating acid, and is then washed, purified and stabilized by conventional methods.

Reynolds numbers, according to Badger and McCabe, Elements of Chemical Engineering, 1936 Ed. page 28, are readily calculated from the following engineering formula:

eynolds Number=QE wherein D=inside diameter of tube in cm.

u=linear velocity of liquid stream in cm./ sec. =density of liquid in g./ml.

=viscosity of liquid in centipoises At Reynolds Number above about 2,100, the flow of a liquid in smQQth. tubes; assumes. a... completely turbulent 4 action which is desirable.

5 character. For the purposes of this invention, completely turbulent flow is not necessary, and successful nitrations have been made at Reynolds Numbers of approximately 1,000. However, to keep the reaction time to a minimum and the efliciency of the heat exchange at a maximum, it is desirable that the Reynolds Number be at least about 2,100.

26 is a conventional heat exchange means, such as a refrigerating brine bath or the like, which is associated with at least part of tubular reactor adjacent the discharge end thereof when it is desired to cool the reao tion mixture prior to discharge of the reaction mixture to a separating zone. However, it is important to note that the invention is not limited in this respect, since as noted hereinb'efore, the invention can be practiced quite satisfactorily with a tubular reactor entirely free of cooling means. On the other hand, under certain circumstances,

-the entire tubular reactor can be surrounded by a brine bath or equivalent heat exchange means, if desired.

However, in a preferred embodiment of the invention, part of the tubular reactor adjacent to the converging feed tubes is not cooled, since this promotes a more rapid re- In this case, the precooled nitrating acid is relied upon to absorb the heat of reaction and control the temperature of the reaction mixture within safe operating limits. In practicing this invention, it has been found that temperatures up to about 70 C. in the reaction mixture during nitration are quite feasible. However, upon substantial completion of the nitration reaction, it is desirable to cool the reaction mixture conmixing of the two reactants, and, although not instantaneous as the prior art would lead one to believe, is nevertheless very rapid under the preferred conditions of the invention, being substantially complete within a matter of one second or less, and seldom if ever longer than about three seconds.

tion zone is of very brief duration, but should be sufficient to accomplish substantial completion of the nitration reaction. The length of the tubular reaction zone for any particular tubular reactor to accomplish the purposes of this invention can be readily ascertained by fixing thermocouples at fixed points along the tubular reactor and noting temperatures. The point of maximum temperature rise corresponds closely with completion of the nitration reaction. Similarly, the length of a tubular cooling zone, when employed, to cool the reaction mixture to any desiredtemperature, also can be readily ascertained by thermocouple readings.

The inside diameter of the tubular reactor will be governed'largely by the projected production throughput capacity desired from the apparatus, keeping in mind the Reynolds Number requirements of the invention.

Although metering pumps, such as gear pumps, are preferred for positively feeding and proportioning the two reactant streams to the tubular reactor, the invention is not limited in this respect, since any known means for accomplishing the positive feed and proportioning of liquid feed streams is equivalent for the purposes of this invention; for example, pressure exerted by a, constant bydraulic head or pressure exerted by gas under constant pressure, pressure accumulators, or the like, or any combination of such means.

The nitration reaction commences immediately upon It. will be apparent, therefore that residence time-of the reaction mixture in the tubular reac- 6' Explosive'liquid nitric acid esters inaccord'anc with this invention include all such esters obtainable by substantially complete nitration of liquid polyhydric alcohols, such as, by way of example, glycerin, ethylene glycol, di ethylene glycol, triethylene glycol, propylene glycol, 1,3 butanediol, 1,2-butanediol, 2,3-butanediol, isopropyl ethylene glycol, nitroisobutylglycerol, glycerol alpha chlorohydr-in, and the like, to obtain glyceryl trinitrate, ethylene glycol dinitrate, diethylene glycol dinitrate, tri ethylene glycol dinitrate, propylene glycol dinitrate, 1,2- butanediol dinitrate, 1,3-butanediol dinitrate, 2,3-butanediol dinitrate, isopropyl ethylene glycol dinitrate, nitroisobutylglycerol trinitrate, glycerol alpha-chlorohydrin'dinitrate, and the like. Mixtures of explosive liquid nitric acid esters obtainable by nitrating mixtures of two or more liquid polyhydric alcohols in any proportion also come within the scope of this invention, as, for example, mixtures of nitroglycerin and nitroglycol. Solid polyhydric alcohols, such as sucrose for example, dissolved in glycerol or glycol, upon nitration in accordance with this invention also form mixtures of explosive liquid nitric acid esters. Nitrating acid according to this invention contains between about 18% and about 40% nitric acid, between about 45% and about 70% sulfuric acid, and between about 11% and about 17% water,-by weight. The nitrating acid may be composed entirely of fresh ingredients or may be made by fortifying spent acid with fresh concentrated nitric acid and fresh concentrated sulfuric acid. When the nitrating acid is prepared by fortifying spent; acid, between about 3 parts and about 8 parts by weight; of spent acid per part of fortifying acid composed, for ex-. ample, of equal parts by weight of concentrated nitric and concentrated sulfuric acid are employed. In general, spent;

.acid in accordance with this invention will contain be-.

tween about 3% and about 32% nitric acid, between, about 48% and about 77% sulfuric acid, between about;

' 15% and about 24% water by weight, and will contain,

small percentages of explosive liquid nitric acid ester and; oxides, usually on' the order of about 2% to 5% ex-- plosive liquid nitric acid ester and from less than 0.01%, to about 0.11% oxides.

In practicing this invention the nitrating acid is pre-.. cooled to a temperature between about +5 C. and: about l0 C. before being fed to the tubular nitrating; zone. Between about 6 parts and about 30' parts by weight of precooled nitrating acid per part of liquid} polyhydric alcohol has been employed in the practice: of this invention. A preferred range is between about 10 parts and about 20 parts by weight precooled nitrating acid per part of polyhydric alcohol.

The following examples set forth some specific embodiments of the invention. It is to be understood, however, that these examples, while illustrative, are not to be construed as a limitation of the invention.

EXAMPLE 1 Preparation of nitroglycerin For this example the tubular reactor consisted of an; uncooled coil of inch inside diameter stainless steel! tubing 470 cm. long constituting the tubular reaction. zone. This was joined at one end thereof by means: of a T tube section, as illustrated in Fig. 2, with the nitrating acid and polyhydric alcohol feed lines, each of inch inside diameter tubing, and at the other end it was joined to a stainless steel cooling coil of 7 inch inside diameter and 1,000 centimeters long in two coiled sections, each surrounded by a refrigerating bath, constituting the tubular cooling zone of the tubular reactor. A coiled section of tubing in the nitrating acid feed line was surrounded by a refrigerating bath to precool the nitrating acid. A constant nitrogen gas pressure of 40 p.s.i. was impressed on the nitrating acid'supply source to feed the nitrating acid to the tubular nitrating zone.

you

' 4 An electrically driven gear pump in the polyhydric alcohol feed line fed the glycerin to the tubular nitrating zone. The .efiluent from the tubular cooling zone of the tubular reactor was discharged into an ice and water drowning bath, from which the nitroglycerin separated by gnavity, after which thenitroglycerin was washed, purified and stabilized by conventional methods. Thermocouples were attached to the two feed lines, and to the tubular reactor at intervals, for measuring the temperature of the reactants, the temperature of the reaction mixture at intervals in the uncooled tubular nitrating zone, and the temperature of the reaction mixture Nitrating acid composition:

HNO percent by wt 20 H 80 percent by wt 68.5 H O. percent by wt 11.5 Feed ratio of nitrating acid to glycerin (by wt.) 13.4 Glycerin feed rate g./m-in 166 Nitrating acid feed rate g./min 2,220 Combined feed rate g./rnin 2,386 Linear rate of flow of reaction mixture cm./sec 338 Density of reaction mixture g./ml Approx. 1.74 Vicosity centipoises Approx. 0.09 Reynolds Number 2,080 Ratio of nitric acid to glycerin (by wt.) 2.97 Temperature of precooled niti'ating acid C 3.7 Maximum temperature reached by' the reaction mixture during nitration C 38.2 Temperature rise in the reaction mixture during nitration C 34.5 Time to complete nitration reaction sec. 0.8 Temperature of the efiluent reaction mixture discharged to the separating zone C 14.4 Percent nitrogen in recovered nitroglycerin (theory=18.5l%) 18.42

EXAMPLE 2' Preparation of nitroglycol The following table lists pertinent data for three different runs wherein ethylene glycol was nitrated employing' substantially the same apparatus and method set forth in Example 1.

Run 1 Run 2 Run 3 Nitrating Acid Composition:

HNO (percent by wt.) 20 19. 5 19. 5 H2804 (percent by wt.) 1. 67. 2 66.0 66.0 H2O (percent by wt.) 12.8 12. l 12. 1 Nitroglycol (percent by Wt.) 0. 0 2. 4 2. 4 Feed Ratio of Nitrating Acid to Glycol (by wt. 12.1 19. 2 24.0 Glycol Feed Rate (g./min.) 191 116 88 Nitrating Acid Feed Rate (g./min.) 2, 311 2, 227 2, 112 Combined Feed Rate (g./min.) 2, 502 2, 343 2, 200 Linear Rate of Flow of Reaction Mixture (cm/sec.) 356 306 332 Density of Reaction Mixture (g./ml.) Approx 1. 76 l. 72 1. 72 Viscosity (centipoises) Approx 0. O9 0. 09 0. 09 Reynolds Number 2, 190 l, 880 2, 040 Ratio of Nitric Acid to Glycol (by wt.) 2. 44 3. 72 4. 86 Temp. of Precooled Nitrating Acid C. -0. 1 3. 1 3. 7 Maximum Temp. Reached by the Reaction Mixture During Nitration C.) 43 8 30. 7 27. 1 Temp. Rise in the Reaction Mixture During Nitration C.) 43. 7 27. 6 23. 4 Time to Complete N itration Reaction (Seconds) 0. 9 0.8 0.9 Temperature of the Efilnent Reaction Mixture Discharged to the Separating Zone C. 17. 6 10.0 8 6 Percent Nitrogen in Recovered Nitroglycol (Theory=l8.42) 18. 41 18. 41 18. 42

EXAMPLE 3 The following table lists pertinent data for three difierent, runs wherein a mixture consisting of 80 parts ethylene glycol and 20 parts glycerin by weight was o nitrated employing substantially the same apparatus and method set forth in Example 1.

Run 1 Run 2 Run 3 Nitrating Acid Composition:

HNO; (percent by wt.) 28 19. 4 23. 2- H2804 (percent by wt.) 62 65. 7 64.1 H20 (percent by wt.) 10 12. 0 10. 3 Mixed Nitroglycol-Nitr0glycerin (percent by wt.) O 2.9 2. 4 Feed Ratio of Nitrating Acid to Mixed Polyhydric Alcohols (by wt.) 17.5 15.0 14. 8 Mixed Polyhydrlc Alcohol Feed Rate (g./

min. 194 144 Nitrating Acid Feed Rate (g./ 3, 395 2, 700 2, 131 Combined Feed Rate (g./min.) 3, 589 2,880 2, 275 Linear Rate of Flow of Reaction Mixture (cm/sec.) 426 412 321 Density of Reaction Mixture (g./rnl.) Approx- 1. 74 1. 74 l. 74' Viscosity of Reaction Mixture (Centipoises) Approx 0. 09 0. O9 0. 09 Reynolds Number 2, 620 2, 540 1, 980 Ratio of Nitric Acid to M ed Polyhydric Alcohols (by wt.) 4. 89 2.91 3. 42 Temp. of Precooled N itrating Acid C.) 4. 5 7. 3 5. 8 Maximum Temp. Reached by Reaction Mixture During Nitration C.) 44. 8 44. 6 40. 7 Temp. Rise in the Reaction Mixture During Nitration C.) 40. 3 37. 3 34.9 Time to Complete Nitration Reaction (Secends) 0.2 0.8 0.9 Temp. of the Efliuent Reaction Mixture Discharged to the Separating Zone C.) l9. 6 21. 4 17.8 Percent Nitrogen in Recovered Mixed N itrated Polyhydric Alcohols (Theory= 18.44%) U, 18. 42 18. 42 18. 42

l. In the manufacture of explosive liquid nitric acid] esters of polyhydric alcohols, the improvement comprising continuously force feeding a stream of liquid saturated aliphatic polyhydric alcohol through a tubular path to an elongated tubular liquid phase reaction zone which is free of obstructions and constrictions, simultaneously and continuously force feeding a stream of precooled nitrating acid through a second tubular path to said elongated tubular liquid phase reaction zone, bringing the separate force-fed streams of polyhydric alcohol and nitrating acid together so that said streams impinge upon each other from opposing directions at sufiicient flow rates to form a turbulent liquid reaction mixture stream in the elongated tubular liquid phase reaction zone, the impingement of said force-fed streams upon each other from opposing directions being the sole means for mixing the polyhydric alcohol with the nitrating acid, continuously advancing the resultant liquid reaction mixture stream through the elongated tubular. liquid phase reaction zone at a flow rate corresponding to a Reynolds Number of at least about 1,000 to reactsubstantially all of the polyhydric alcohol with the nitrating acid to form explosive liquid nitric acid ester in saidelongated tubular liquid phase reaction zone, thereafter continuously dischargingthe liquid reaction mixture stream into a separating zone and there continuously separating explosive liquid'nitric acid ester of polyhydric alcohol from 9 water by weight, the ratio of said nitrating acid to said polyhydric alcohol being between about 6 parts and about 30 parts per part of polyhydric alcohol by weight.

4. The process in accordance with claim 1 wherein the polyhydric alcohol is glycerin.

5. The process in accordance with claim 1 wherein the polyhydric alcohol is ethylene glycol.

6. The process in accordance with claim 1 wherein the polyhydric alcohol is a mixture of glycerin and ethylene glycol.

7. The process in accordance with claim 1 wherein the tubular reaction zone is uncooled and the temperature of the reaction mixture in said tubular reaction zone is controlled by regulating the temperature of the precooled nitrating acid and by regulating the proportions, respectively, of said nitrating acid and of said polyhydric alcohol which are mixed together by impingement to form said reaction mixture.

8. In the manufacture of explosive liquid nitric acid esters of polyhydric alcohols, the improvement comprising continuously force feeding a stream of liquid saturated aliphatic polyhydric alcohol through a tubular path to an uncooled elongated tubular liquid phase reaction zone which is free of obstructions and constrictions, simultaneously and continuously force feeding a stream of precooled nitrating acid through a second tubular path to said uncooled elongated tubular liquid phase reaction zone, bringing the separate force-fed streams of polyhydric alcohol and nitrating acid together so that said streams impinge upon each other from opposing directions at suflicient flow rates to form a turbulent liquid reaction mixture stream in the uncooled elongated tubular liquid phase reaction zone, the impingement of said force-fed streams upon each other from opposing directions being the sole means for mixing the polyhydric alcohol with the nitrating acid, continuously advancing the resultant liquid reaction mixture stream through the uncooled elongated tubular liquid phase reaction zone at a flow rate corresponding to a Reynolds Number of at least about 1,000 to react substantially all of the polyhydric alcohol with the nitrating acid to form explosive liquid nitric acid ester in said uncooled elongated tubular liquid phase reaction zone, continuously passing the liquid reaction mixture stream from the uncooled elongated tubular liquid phase reaction zone into an elon gated tubular cooling zone and advancing said liquid reaction mixture stream through said cooling zone at a. flow rate corresponding to a Reynolds Number of at least about 1,000 to cool said liquid reaction mixture stream, thereafter continuously discharging the cooled liquid reaction mixture stream from the elongated tubular cooling zone into a separating zone and there continuously separating explosive liquid nitric acid ester of polyhydric alcohol from spent nitrating acid.

References Cited in the file of this patent UNITED STATES PATENTS 125,635 Volney Apr. 9, 1872 449,687 Maxim Apr. 7, 1891 2,363,834 Crater Nov. 28, 1944 2,579,474 Crawford Dec. 25, 1951 2,606,919 Crawford Aug. 12, 1952 2,737,522 Nilsson Mar. 6, 1956 2,787,521 Roberts et a1. June 2, 1956 OTHER REFERENCES Chemical Engineers Handbook, 3rd edition (1950), page 1203, McGraw-Hill Book Co., NY. 

1. IN THE MANUFACTURE OF EXPLOSIVE LIQUID NITRIC ACID ESTERS OF POLYHYDRIC ALCOHOLS, THE IMPROVEMENT COMPRISING CONTINUOUSLY FORCE FEEDING A STREAM OF LIQUID SATURATED ALIPHATIC POLYHYDRIC ALCOHOL THROUGH A TUBULAR PATH TO AN ELONGATED TUBULAR LIQUID PHASE REACTION ZONE WHICH IS FREE OF OBSTRUCTIONS AND CONSTRICTIONS, SIMULTANEOUSLY AND CONTINUOUSLY FORCE FEEDING A STREAM OF PRECOOLED NITRATING ACID THROUGH A SECOND TUBULAR PATH TO SAID ELONGATED TUBULAR LIQUID PHASE REACTION ZONE, BRINGING THE SEPARATE FORCE-FED STREAMS OF POLYHYDRIC ALCOHOL AND NITRATING ACID TOGETHER SO THAT SAID STREAMS IMPINGE UPON EACH OTHER FROM OPPOSING DIRECTIONS AT SUFFICIENT FLOW RATES TO FORM A TURBULENT LIQUID REACTION MIXTURE STREAM IN THE ELONGATED TUBULAR LIQUID PHASE REACTION ZONE, THE IMPINGEMENT OF SAID FORCE-FED STREAMS UPON EACH OTHER FROM OPPOSING DIRECTIONS BEING THE SOLE MEANS FOR MIXING THE POLYHYDRIC ALCOHOL WITH THE NITRATING ACID, CONTINUOUSLY ADVANCING THE RESULTANT LIQUID REACTION MIXTURE STREAM THROUGH THE ELONGATED TUBULAR LIQUID PHASE REACTION ZONE AT A FLOW RATE CORRESPONDING TO A REYNOLDS NUMBER OF AT LEAST ABOUT 1,000 TO REACT SUBSTANTIALLY ALL OF THE POLYHYDRIC ALCOHOL WITH THE NITRATING ACID TO FORM EXPLOSIVE LIQUID NITRIC ACID ESTER IN SAID ELONGATED TUBULAR LIQUID PHASE REACTION ZONE, THEREAFTER CONTINUOUSLY DISCHARGING THE LIQUID REACTION MIXTURE STREAM INTO A SEPARATING ZONE AND THERE CONTINUOUSLY SEPARATING EXPLOSIVE LIQUID NITRIC ACID ESTER OF POLYHYDRIC ALCOHOL FROM SPENT NITRATING ACID. 